Boris Johnson made a flying visit to Glasgow on his leadership campaign trip to Scotland.

Ahead of a hustings in Perth, seeking votes in front of Conservative Party members, he stepped into overalls and donned a hard hat for a tour of the BAE Systems shipyard in Govan.

Mr Johnson was helicoptered into the city to a nearby police helipad before being driven to the yard.

He met workers and apprentices and said he was proud to have played a “small part” in promoting the Type 26 frigates, designed in Glasgow, and currently being built on the Clyde.

Mr Johnson is the favourite in the leadership contest against Jeremy Hunt, but he has not been as popular with Tory figures north of the Border as he is in England.

While Mr Johnson was heading north, Scottish Conservatives’ leader Ruth Davidson declined the opportunity to give him her backing, stating only that she would support the Prime Minister “of whatever stripe”, stating “when the Prime Minister does well the country does well”.

The shipyard is a favoured visit of UK Cabinet ministers to come north and pledge their support for the union in front of Royal Navy warships under construction.

Standing on the banks of the River Clyde, Mr Johnson used his visit to state his “passion” for the Union and to oppose a second independence referendum. While not declaring outright he would block a second referendum, he said the matter was decided in 2014.

As both he and Mr Hunt attempt to outdo each other on protecting the future of the United Kingdom, Mr Johnson said there shouldn’t be another vote.

He said: “What I would say is we had a referendum in 2014. I remember it well.

I obviously campaigned on the side of the UK and the Union because I believe in it passionately and was delighted to see it win. “It was a decisive win and I don’t think there’s any need, speaking personally, to see any more referendum on that subject for this generation.

“We did it then. I think people voted then, they were assured that their votes were decisive. They were told this was a once-in-a-generation thing and we should stick to that.

“I think we should stick to that promise.”

After a tour of the yard and meeting workers on HMS Glasgow, the first of the City Class Type 26 Frigates to be built, he claimed that shipbuilding can benefit from a “sensible” Brexit.

Mr Johnson said when he was foreign secretary he was part of the “sales team” promoting the frigates abroad.

He said: “There may be an opportunity to get more shipbuilding done.

“It drives high-quality jobs and produces and regenerates whole areas of the country.

“It may be possible while seeking value for the taxpayer with fleet ships, for example, to do things that will drive even more shipbuilding.”

He said that Brexit, rather than increasing support for independence, would make it more difficult for the SNP to argue for separation.

Asked what was more important the Union or Brexit he said: “The Union must come first and I believe also, as it happens, a good deal, sensible Brexit will strengthen the Union.

“If we come out of the EU in the way we all hope and we get a good deal, we are able to start doing free trade deals with our friends around the world.

“What is the SNP, the breakaway party, going to say then? “Are they really going to want Scotland to join the euro, to join [the] Schengen [Area] to submit to the whole panoply of EU laws and is it going to be the centrepiece of the SNP campaign?

“It doesn’t sound like the winning formula to me and I think actually far from weakening the Union a sensible Brexit will spike the guns of the SNP and strengthen the Union.”

On his visit he also stated his opposition to any decriminalisation of drugs and pledged an extra £1billion of cash for frontline policing.

He said Scotland would benefit from around £80 million of that in Barnet consequentials.

He added: “What I would urge is that the SNP makes sure their share of that does indeed go on frontline policing.

“We should be helping the police crack down on the drugs gangs. “They are out of control, getting young kids to risk their lives for the sake of the drugs market and I want to see more law enforcement a tougher approach.”